1. Field of the Invention
The present general inventive concept relates to a toner for developing an electrostatic charge image used for development of an electrostatic latent image, and an apparatus and method for forming the image using the same.
2. Description of the Related Art
Toner particles suitable for use in an electrophotographic process and an electrostatic image recording process may be largely classified into toner particles prepared by using a pulverization method and toner particles prepared by using a polymerization method.
For toners manufactured by pulverization, there is a wide selection of resins available for use, and a desired toner may be relatively easily manufactured. However, because it is difficult to precisely control the particle size and particle size distribution of toner particles and the toner structure, the particle shape is irregular, and the particle size distribution is wide, major properties required for a toner, such as chargeability, transferability, fixability, developability, fluidity, fine dot reproducibility, storability, etc., are poor, and it is difficult to independently design these properties. In addition, image defects, such as streaking, image contamination, deterioration of fixing properties such as offset, and reduction in gloss, may occur. As a result, manufacturing such toners generally includes multiple processes, high energy consumption, and high costs.
Recently, research has been conducted into a method of developing a polymerized toner, whereby the particle diameter is easily controllable and which does not require a complex manufacturing process, such as size classification. When a toner is manufactured by using this polymerization method, a polymerized toner having a desired particle size and particle size distribution may be obtained, without pulverizing or size classification. Since a polymerized toner has a smaller particle diameter and a narrower particle size distribution, as compared to a toner manufactured by a pulverization method, the polymerized toner is advantageous in that it has high chargeability, transferability, and charge stability, good dot and line reproducibility, low toner consumption, and high image quality. In particular, the polymerization method provides the ability to control the shape of toner particles, which may range from an almost perfectly spherical to potato-shaped.
A toner with spherical particles may be transferred to paper with uniform thickness and concentration, and has a low incidence of toner reverse polarity. However, spherical toner particles are difficult to clean. To compensate for this cleanability deficiency, toners with potato-shaped particles are typically used.
In particular, to accommodate modern tendencies for miniaturization, low price realization, and environmental concerns, while providing for full-colorization, high speed, and high quality images in a printer, a toner shape and surface control technology to satisfy the properties of a toner is becoming increasingly important. For example, the frequency of shear strain imposed on a toner has increased due to higher speed operations. Therefore, a high-durability toner is needed, and toner surface treatment technology is needed to enhance the charging uniformity and transfer efficiency of a toner, in order to reduce the amount of residual toner not transferred during the transfer process.
Recently, tandem-mode development methods have been widely used, due to the higher speeds of printers and copying machines. In order to obtain a high quality image using tandem-mode development methods, high charge stability, transfer efficiency, and cleanability, are needed. In order to enhance charge stability, transfer efficiency, and cleanability, the selection of an additive for treating toner particle surfaces is important. Additives confer fluidity to resin particles, to improve toner supplying ability, and adhere to toner particle surfaces to confer stable charging performance. In addition, additives reduce the surface adhesion of an electrostatic latent image bearing member, to greatly influence toner cleanability.
However, it is difficult to stably secure all the above qualities using conventional inorganic particles as surface treatment agents. In particular, when a toner with a small average particle diameter is used for high image quality applications, it difficult to achieve sufficient performance using a conventional inorganic additive. As the toner particle diameter decreases, toner fluidity is reduced. Accordingly, a large amount of inorganic external additive is generally used. However, these inorganic additives tend to be easily liberated from toner surfaces or may be embedded in toner surfaces, due to stress caused by friction between a toner supply roller and a cleaning blade, agitation in a developing machine, etc. When an external additive is liberated or embedded, the fluidity of toner particles is reduced, resulting in a reduction in the ability to supply toner and an increase of adhesion to the developing roller, leading to a rapid reduction in developability and durability.